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Re: Gravity needs NO Matter

Cross-posted to 2 groups.

Followups directed to: sci.physics.relativity

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Y.Porat wrote in <news:sci.physics>:

> On Saturday, January 30, 2016 at 3:07:31 PM UTC+2, Thomas 'PointedEars'
> Lahn wrote:

Attribution _line_, not attribution novel.

>> benj wrote in <news:sci.physics.relativity> and <news:sci.physics>:
>> > This is why you always need "authorities" to tell you what is
>> > "in". I presume you have a nice stubbly growth of hair on your face to
>> > be like all your Hollywood heros these days!
>> > 
>> > So you can't just look at the equation F = ma and notice that m is the
>> > factor between F and a? Are you REALLY that ignorant? Go back to your
>> > wooden toys.
>> 
>> You just do not realize that the definition of a “relativistic mass”
>> m_rel that increases with relative speed v according to
>>=======================================

I did not post those delimiters; you have forged the quotation.

>>       E = m_rel c²
> ===================================
> i can write
> m babayaga c^2
>  as well as you write
> m rel

I wrote “m_rel” instead, the underscore indicating a following subscript.

> why not??
> the paper can suffer anything you mumble on it

The symbols that I have used have a specific meaning, though, and that 
meaning differs as the symbols differ (as it should be).  AISB, m_rel 
specifies the previous, now-obsolete, concept of a velocity-dependent (not 
invariant) relativistic mass.

Besides, “babayaga” as-is is not an appropriate symbol in a physics equation 
as there would always be doubt whether it would be equivalent to b²a⁴yg.

> --------
>>   m_rel = γm₀ = m₀∕√(1 − (v∕c)²)
> while  (1 − (v∕c)²
> you get while v = c
> you get infinity !!

Not quite; the value for m_rel *approaches* infinity (m_rel → ∞) as v 
*approaches* c (v → c), and m_rel is not defined at v = c.  You also get 
that with the aforementioned (and futher below expanded) equation for 
relativistic momentum,

  p = γ m v = m v∕√(1 − (v∕c)²).

One of the conclusions from special relativity is that no object with 
m = m₀ > 0 can move at c as for that it would have to be supplied with an 
infinite amount of extra energy.

It can be seen even better in the equation for relativistic kinetic energy,

  E_k = m γ c² − m c² = m c²∕√(1 − (v/c)²) − m c²

where m c²∕√(1 − (v/c)²) → ∞ as v → c.  So, IOW, “the work expended 
accelerating an object [with non-zero mass; the ed.] from rest approaches 
infinity as the velocity approaches the speed of light.”

<https://en.wikipedia.org/wiki/Kinetic_energy#Relativistic_kinetic_energy_of_rigid_bodies>

> […]
>> was a rather confusing concept (especially to students) that Einstein
>> himself deprecated later.  It is *easier* to consider that what really
>> increases with relative speed is the total *energy*
> ---------
> common man

Did you mean to write “come on, man” instead?

> =====that is your private story !!

No, it is not.  Read the quotations that I posted and follow the references.

[repaired quotation]
 
>> that an object has (thus the work that it can do, as its kinetic energy
>> must be increased in order to put it into relative motion; the total
>> energy in relative motion then also called “relativistic energy” as
>> opposed to “rest energy”, its energy in its rest frame), so that there is
>> only mass m = m₀ (previously called “rest mass”, i.e. the mass of an
>> object in its rest frame), and that the energy– momentum relation
>> 
>>   E = √((mc²)² + (pc)²),
> ================================
> another stupidity cheating !!

There is no cheating, see e.g. 
<https://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation#Norm_of_the_four-momentum>.
 
> THAT FORMULA IS FOR -
> LISTEN CAREFULLY PARROT

Your Shift key appears to be stuck.

> IT IS FOR A **MIXTURE* OF ENERGY PLUS PARTICLES !!

Nonsense.  Energy is a *property* of a physical object such as a particle; 
it is not a separate entity.  Every physical object has an energy; objects 
that have non-zero mass have a rest energy in their rest frame of reference. 
When they are moving, that is, when their velocity relative to a frame of 
reference that is not co-moving with them is not zero, and so their momentum 
is not zero, they have gained kinetic energy for an observer whose rest 
frame is that frame of reference.
 
> 2
> where do you see in m of momentum
> anything relativistic ???
> any relativistic coefficient ???

See below.
 
> =====
>> 
>> derived from the norm of the four-momentum P⃗ = (E∕c, p⃗), holds both for
>> objects with non-zero (rest) mass and objects with zero (rest) mass such
>> as photons, whereas for m > 0 and 0 < v < c
>> 
>>    p = γmv = mv∕√(1 − (v∕c)²),
> =============================
> that is as well your mathematical cheating
> ie
> one cheating based on another same cheating

There is no cheating.  γ (\gamma) is the Lorentz factor, *the* "relativistic 
coefficient".  In full (and less ambiguous), the above is:

  p = γ m v

  γ = 1∕√(1 − (v∕c)²)

  p = 1∕√(1 − (v∕c)²) × mv

  p = m v∕√(1 − (v∕c)²). ∎

>> and for photons (m = 0)
> =======================
> imbecileparrot
> see the formula for photon energy:
> E=hf
> that was found experimentally 5 years before any relativity!!

One of the good things about special relativity is that it confirms Planck’s 
equations (and probably Einstein would not have published “On the 
Electrodynamics of Moving Bodies” and subsequent works on special relativity 
like this if he had found that Minkowski spacetime would not support 
Planck’s quantum idea that he [Einstein] just confirmed about three months 
earlier in “On a Heuristic Viewpoint Concerning the Production and 
Transformation of Light”).

Let us assume that the energy–momentum relation

  E = √((m c²)² + (p c)²)      (1)

holds for all physical objects.

For a photon, we know that

  p = ℎ f∕c,                   (2)

and we assume for it

  m := 0.                      (3)

Applying (2) and (3) to (1) yields

  E = √((0 × c²)² + (ℎ f∕c × c)²)

  E = √(0         + (ℎ f)²)

  E = √(ℎ f)²

  E = ℎ f. ∎  (Planck–Einstein relation)

One can also easily see that for a photon

  E = ℎ f = p c.


F'up2 sci.physics.relativity

PointedEars
-- 
Two neutrinos go through a bar ...

(from: WolframAlpha)

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Thread

Gravity needs NO Matter Juan Sebastián <jseb@montserrat.info> - 2016-01-29 10:43 +0000
  Re: Gravity needs NO Matter Odd Bodkin <bodkinodd@gmail.com> - 2016-01-29 07:40 -0600
    Re: Gravity needs NO Matter Juan Sebastián <jseb@montserrat.info> - 2016-01-29 13:50 +0000
    Re: Gravity needs NO Matter benj <none@gmail.com> - 2016-01-29 12:22 -0500
      Re: Gravity needs NO Matter Odd Bodkin <bodkinodd@gmail.com> - 2016-01-29 11:28 -0600
        Re: Gravity needs NO Matter benj <none@gmail.com> - 2016-01-29 13:41 -0500
          Re: Gravity needs NO Matter Odd Bodkin <bodkinodd@gmail.com> - 2016-01-29 13:36 -0600
            Re: Gravity needs NO Matter benj <none@gmail.com> - 2016-01-30 02:30 -0500
          Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-30 14:07 +0100
            Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-30 09:32 -0800
              Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-30 20:19 +0100
                Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-30 15:37 -0800
                Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-31 18:15 +0100
                Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-02-06 10:23 -0800
                Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-02-06 11:14 -0800
                Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-06 22:24 +0100
                Re: Gravity needs NO Matter Éibhear <eibhear@no-email.net> - 2016-02-06 21:28 +0000
                Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-07 10:00 +0100
            Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-01 21:50 +0100
              Re: Gravity needs NO Matter shan <shan@enterapps.org> - 2016-02-05 21:43 +0000
  Re: Gravity needs NO Matter Sam Wormley <swormley1@gmail.com> - 2016-01-29 08:13 -0600
    Re: Gravity needs NO Matter Maciej Woźniak <mlwozniak@wp.pl> - 2016-01-29 16:44 +0100
  Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-29 11:03 -0800
    Re: Gravity needs NO Matter Juan Sebastián <jseb@montserrat.info> - 2016-01-29 19:35 +0000
  Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-29 16:04 -0800

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